1. Field of the Invention
The present invention relates to an ink-jet head, and, more specifically, to a structure of an ink-jet head in an ink-jet recording apparatus and a method of making such an ink-jet head.
2. Description of the Related Art
On-demand-type ink-jet heads are widely known. As a result of the demand for performing printing in color, and, for high-quality printing and high-speed printing, there has been a requirement that the number of nozzles and the nozzle density of ink-jet heads be increased.
One conventional ink-jet head has a structure and operation which are simple and which achieves high ink-jet-head density. This ink-jet head has a system in which an electrostatic force is produced between a diaphragm and an electrode, the diaphragm is deformed, and a liquid is pressurized due to the restoration force of the diaphragm so that the liquid is fired. A diffused layer in a Si substrate is used as the electrode.
Japanese Laid-Open Patent Application No. 6-55732 discloses an ink-jet head in which a metal layer is formed so that the resistance of a diaphragm is reduced without reducing the resistance of a Si substrate in order to provide a driving device in the Si substrate which is integral with the diaphragm.
In such an electrostatic-type ink-jet head, ink is fired using the restoration force produced due to elasticity of the diaphragm. In this ink-jet head, the short-side-direction width of the diaphragm must be narrowed due to the increase in the nozzle density. The displacement of the diaphragm is proportional to the fourth power of the short-side length thereof. Therefore, the driving voltage must be very high in order to obtain sufficient displacement of the diaphragm. For example, in a case where the short-side length is 55 .mu.m, the driving voltage reaches a voltage of about 150 V. When the nozzle density increases, the total number of nozzles increases. Therefore, when the cost of the driving circuit for each nozzle increases due to the increase in the driving voltage, the total cost increases greatly.